Systems and modules for testing uninterruptible power supply (ups) systems with multiple ups module

ABSTRACT

A method of operating an Uninterruptible Power Supply (UPS) system can be provided by activating an idle state for a UPS module included in the UPS system and providing a UPS module test input to the UPS module in the idle state. A UPS module test response can be provided from the UPS module in the idle state, to the UPS module test input. The UPS module test response can be compared to a predetermined UPS module test response and the UPS module can be identified as a potentially faulty UPS module responsive to determining that the UPS module test response varies from the predetermined UPS module test response by more than a threshold value.

RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/974,904; filed Dec. 18, 2015, which is a divisional of U.S.patent application Ser. No. 13/717,740 filed Dec. 18, 2012 in the UnitedStates Patent Office, the disclosures of which are hereby incorporatedby reference in their entireties.

BACKGROUND

The present invention relates to uninterruptible power supply systems(UPS), and more particularly, to testing UPS systems.

UPS systems are commonly used in installations such as data centers,medical centers and industrial facilities to provide backup power tomaintain operation in event of failure of the primary utility supply.These UPS systems often have an “on-line” configuration includingcomponents, such as, a rectifier and inverter coupled by a DC link thatis also coupled to an auxiliary power source, such as a battery, fuelcell or other energy storage device. UPS systems may include two or moreUPS modules, each of which may include the components described above.The UPS modules commonly are designed to operate in parallel to providescalable power capacity, e.g., the UPS modules may be coupled in commonto an AC source, a DC source (e.g., a battery) and to a load.

UPS systems typically may be configured for testing when, for example, adiagnostic is run, which may result in the UPS systems being broughtoff-line. Various UPS arrangements are discussed further in, forexample, U.S. Pat. No. 7,265,458 to Edelen et al., U.S. Pat. No.7,403,364 to Anderson et al., U.S. Pat. No. 7,583,109 to Oughton Jr. etal., and U.S. Pat. No. 7,948,778 to Pfitzer et al., the disclosures ofeach of which are incorporated herein in their entireties.

SUMMARY

Embodiments according to the present invention can provide methods,systems, and modules for testing UPS systems with multiple UPS modules.Pursuant to these embodiments, a method of operating a UPS system can beprovided by activating an idle state for a UPS module included in theUPS system and providing a UPS module test input to the UPS module inthe idle state. A UPS module test response can be provided from the UPSmodule in the idle state, to the UPS module test input. The UPS moduletest response can be compared to a predetermined UPS module testresponse and the UPS module can be identified as a potentially faultyUPS module responsive to determining that the UPS module test responsevaries from the predetermined UPS module test response by more than athreshold value.

In some embodiments according to the invention, identifying the UPSmodule as a potentially faulty UPS module can be provided by comparingthe UPS module test response to a predetermined UPS module test responseand transmitting a service indicator that identifies the UPS module aspotentially faulty. In some embodiments according to the invention, theUPS module test response varies from the predetermined UPS module testresponse by an amount associated with a faulty power supply in the UPSmodule, a faulty fan in the UPS module, a faulty power conversioncircuit in the UPS, a faulty DC link capacitor, a faulty invertercircuit, a faulty rectifier circuit, a faulty DC-DC converter circuit, afaulty output filter circuit, or any combination thereof.

In some embodiments according to the invention, the UPS module testresponse varies from the predetermined UPS module test response by anamount associated with a faulty component included in the UPS module,the faulty component being configured to operate when the UPS module isin the idle state.

In some embodiments according to the invention, activating the idlestate for the UPS module includes configuring the UPS module to provideno power to the load. In some embodiments according to the invention,configuring the UPS module to provide no power to the load can includeopening a contactor located between the load and an inverter circuitincluded in the UPS module or electrically isolating an output of arectifier circuit from the load.

In some embodiments according to the invention, the method can furtherinclude preventing the UPS module from providing power to the loadresponsive to identifying the UPS module as the potentially faulty UPSmodule. In some embodiments according to the invention, the method canfurther include identifying the UPS module as a functional UPS moduleresponsive to determining that the UPS module test response varies fromthe predetermined UPS module test response by less than the thresholdvalue and deactivating the idle state for the UPS module.

In some embodiments according to the invention, activating the idlestate for the UPS module comprises activating the idle state for a firstUPS module responsive to determining that a second UPS module includedin the UPS system is configured to provide the power to the load, whilethe first UPS module is in the idle state.

In some embodiments according to the invention, a method of operating anUninterruptible Power Supply (UPS) system, and be provided by activatingan idle state for a UPS module included in the UPS system. A UPS moduletest power input is provided to the to the UPS module in the idle stateand a UPS module test power response to the UPS module test power inputis provided. The UPS module test power response can be compared to apredetermined UPS module test power response.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a hierarchal arrangement of UPSsystems in embodiments according to the invention.

FIG. 2 is a block diagram illustrating a UPS system included in thehierarchy shown in FIG. 1 in some embodiments according to theinvention.

FIG. 3 is a flow chart that illustrates operations of UPS modules andsystems in some embodiments according to the invention.

FIG. 4 is a block diagram illustrating a UPS module included in a systemshown in FIG. 2 some in embodiments according to the invention.

FIGS. 5A and 5B are graphs indicating discharging and chargingcharacteristics, respectively, of a capacitor in some embodimentsaccording to the invention.

FIG. 6 is a graph illustrating bleed-down characteristics of an outputfilter circuit in some embodiments according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION

Specific exemplary embodiments of the inventive subject matter now willbe described with reference to the accompanying drawings. This inventivesubject matter may, however, be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein;rather, these embodiments are provided so that this disclosure will bethorough and complete, and will fully convey the scope of the inventivesubject matter to those skilled in the art. In the drawings, likenumbers refer to like elements. It will be understood that when anelement is referred to as being “connected” or “coupled” to anotherelement, it can be directly connected or coupled to the other element orintervening elements may be present. As used herein the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventivesubject matter. As used herein, the singular forms “a”, “an” and “the”are intended to include the plural forms as well, unless expresslystated otherwise. It will be further understood that the terms“includes,” “comprises,” “including” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive subject matterbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of thespecification and the relevant art and will not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

As will be appreciated by one skilled in the art, aspects of the presentdisclosure may be illustrated and described herein in any of a number ofpatentable classes or contexts including any new and useful process,machine, manufacture, or composition of matter, or any new and usefulimprovement thereof. Accordingly, aspects of the present disclosure maybe implemented entirely hardware, entirely software (including firmware,resident software, micro-code, etc.) or combining software and hardwareimplementation that may all generally be referred to herein as a“circuit,” “module,” “component,” or “system.” Furthermore, aspects ofthe present disclosure may take the form of a computer program productcomprising one or more computer readable media having computer readableprogram code embodied thereon.

Any combination of one or more computer readable media may be used. Thecomputer readable media may be a computer readable signal medium or acomputer readable storage medium. A computer readable storage medium maybe, for example, but not limited to, an electronic, magnetic, optical,electromagnetic, or semiconductor system, apparatus, or device, or anysuitable combination of the foregoing. More specific examples (anon-exhaustive list) of the computer readable storage medium wouldinclude the following: a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an appropriateoptical fiber with a repeater, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device. Program codeembodied on a computer readable signal medium may be transmitted usingany appropriate medium, including but not limited to wireless, wireline,optical fiber cable, RF, etc., or any suitable combination of theforegoing.

Computer program code for carrying out operations for aspects of thepresent disclosure may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C #, VB.NET,Python or the like, conventional procedural programming languages, suchas the “C” programming language, Visual Basic, Fortran 2003, Perl, COBOL2002, PHP, ABAP, dynamic programming languages such as Python, Ruby andGroovy, or other programming languages. The program code may executeentirely on the user's computer, partly on the user's computer, as astand-alone software package, partly on the user's computer and partlyon a remote computer or entirely on the remote computer or server. Inthe latter scenario, the remote computer may be connected to the user'scomputer through any type of network, including a local area network(LAN) or a wide area network (WAN), or the connection may be made to anexternal computer (for example, through the Internet using an InternetService Provider) or in a cloud computing environment or offered as aservice such as a Software as a Service (SaaS).

Aspects of the present disclosure are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of thedisclosure. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor or control circuit of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmableinstruction execution apparatus, create a mechanism for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that when executed can direct a computer, otherprogrammable data processing apparatus, or other devices to function ina particular manner, such that the instructions when stored in thecomputer readable medium produce an article of manufacture includinginstructions which when executed, cause a computer to implement thefunction/act specified in the flowchart and/or block diagram block orblocks. The computer program instructions may also be loaded onto acomputer, other programmable instruction execution apparatus, or otherdevices to cause a series of operational steps to be performed on thecomputer, other programmable apparatuses or other devices to produce acomputer implemented process such that the instructions which execute onthe computer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

As described herein, in some embodiments according to the invention, aUPS module included in a UPS system can be placed in an idle state sothat various tests can be carried out on the UPS module, while the UPSsystem continues to provide power to a load using other UPS modules. Forexample, in some embodiments according to the invention, a UPS systemmay include multiple UPS modules, each of which can be configured toprovide power to a load when the respective module is operating in anactive state. When, however, the UPS system determines that the load canbe carried by less than all of the UPS modules, selected ones of the UPSmodules can be placed in an idle state, whereupon diagnostic tests canbe performed on the UPS module in the idle state. In the idle state,various diagnostic tests can be performed on the UPS module which maynot otherwise be realizable when the UPS module provides power to theload. In other words, once the UPS module is placed in the idle state,the UPS module may be manipulated by the diagnostics in ways that wouldpossibly interrupt provisioning of power of the load.

In some embodiments according to the invention, diagnostics can becarried out on the UPS module in the idle state focusing on power valuesof the UPS module and/or power values associated with individual systemsor circuits within the UPS module in the idle state. For example, insome embodiments according to the invention, a total power test can becarried out on the UPS module when in the idle state, the value of whichcan be compared to a predetermined power value associated with a known,non-faulty, UPS module. Other diagnostic tests can be performed on thedifferent subsystems and circuits within the UPS module, such as arectifier circuit, an inverter circuit, a DC-DC converter circuit, anoutput filter circuit, and a DC link capacitor, etc. Similarly, thosetest results can be compared to predetermined values associated with thecircuits or systems under test to determine if the circuits or systemsare likely faulty.

FIG. 1 is a block diagram illustrating a hierarchal UPS system 100 insome embodiments according to the invention. According to FIG. 1, theUPS system 100 can include multiple UPS systems 105-1 to N. Each of theUPS systems 105-1 to N is coupled to an AC input bus which can provideeach of the UPS systems 105-1 to N with AC power, both for conductinginternal operations of the respective UPS system, as well as providingpower to the load. It will be understood that various ones of the UPSsystems may receive AC power via various distribution paths, such asswitches, panels, etc.

As further shown in FIG. 1, the UPS system 100 includes a UPS systemscontrol circuit 110 which is operatively coupled to each of the UPSsystems 105-1 to N. The UPS systems control circuit 110 can transmit(among other things) diagnostic control data to each of the UPS systems105-1 to N, and can receive corresponding diagnostic data/status fromeach of the systems. Accordingly, the UPS systems control circuit 110can cause each of the UPS systems 105-1 to N to enter an idle state,whereupon diagnostic operations can be carried out within the respectiveUPS system 105-1 to N. In addition, each of the UPS systems 105-1 to Ncan provide diagnostic data/status to the UPS systems control circuit110 indicating, for example, the results of the completed diagnostics.In some embodiments according to the invention, it will be understoodthat the UPS systems 105-1 to N can provide partial diagnosticdata/status, as the diagnostics progress.

During provisioning of power to the load, the UPS systems controlcircuit 110 can, for example, instruct the UPS system 105-1 to enter anidle state while maintaining UPS systems 105-2 to N in the active state,so that the load coupled thereto is provided adequate power. It will befurther understood that the UPS system 105-1 may provide no power to theload when in the idle state. The UPS systems control circuit 110 canfurther control the UPS system 105-1 to perform diagnostic operationswhile in the idle state and return diagnostic data/status. Uponcompletion, the UPS systems control circuit 110 may determine whetherthe UPS system 105-1 includes faulty components or subsystems, and tothe extent that UPS system 105-1 should remain idle. Alternatively, theUPS systems control circuit 110 may determine, based on the diagnosticdata/status, that the UPS system 105-1 is operational and may exit theidle state, to provide power to the load. It will be understood thateach of other the systems 105-2 to N, can also be controlled asdescribed above.

Still further, the UPS systems control circuit 110 can aggregatediagnostic data/status from the UPS systems 105-1 to N and forward suchaggregated information to a server 120, which may operate at a higherlevel in the hierarchy in which the UPS system 100 is located. It willbe understood that the aggregated diagnostic information can be providedto the server 120 via any available network 115, such as the Internet,an intranet, or other networks. Server 120 may, in turn, aggregate datafrom other UPS systems, which may be located at the same site or over awider region.

Although the embodiments described with reference to FIG. 1 illustratethe initiation of the idle state and diagnostics via the control circuit110 located within the system 100, it will be understood that higherlevel circuits may initiate the idle state for the UPS system shown, andreceive the associated diagnostic data/status.

FIG. 2 is a block diagram illustrating a representative UPS system 105shown in FIG. 1 in some embodiments according to the invention.According to FIG. 2, the UPS system 105 includes multiple UPS modules205-1 to N, each of which receives the AC input and is configured toprovide power to the load under control of a UPS system control circuit210. It will be understood that the UPS system control circuit 210 canbe analogous to the UPS systems control circuit 110 shown in FIG. 1operating at an upper level of the hierarchy. Still further, the UPSsystem control circuit 210 can transmit diagnostic control data to eachof the UPS modules 205-1 to N and receive diagnostic data/statusindicating the results of the diagnostics. It will also be understoodthat the diagnostic control provided by the UPS control circuit 210 canbe initiated by the UPS systems control circuit 110 shown in FIG. 1 and,in turn, the diagnostic data/status returned from the UPS modules 205-1to N can be forwarded to the UPS systems control circuit 110. In stillother embodiments according to the invention, the diagnostic control anddiagnostic data/status can be maintained at the level of the UPS system105. In other words, the diagnostics may operate under the control ofany level of the hierarchy in the system 100, and, specifically, mayoriginate and be maintained in each of the UPS systems 105.

FIG. 3 is a flow chart that illustrates operations of a UPS module 205operating in the UPS system 105 in some embodiments according to theinvention. According to FIG. 3, the UPS module 205 enters the idle state(block 300), under control of either the UPS control circuit 210 oranother UPS control circuit within the hierarchy. A UPS module testinput is applied to the UPS module operating in the idle state (block305).

The UPS module 205 in the idle state provides a response to the UPSmodule test input (block 310), which is compared to a predetermined UPStest module response (block 315). In some embodiments according to theinvention, the predetermined UPS test module response can be based uponmeasurements or calculations that are associated within known good UPSmodules or components thereof. For example, in some embodimentsaccording to the invention, the UPS module test input may to be provideAC power at an input to the rectifier circuit, whereas the UPS moduletest response can be the measured power drawn at the input. Stillfurther, the predetermined UPS test module response can be a nominalpower drawn at the AC input by a UPS module, known not to be faulty.

Still referring to FIG. 3, the difference between the predetermined UPStest module response and the measured test response can be determinedand compared to a threshold value, beyond which it may be consideredthat the UPS module (or circuit) may be faulty (block 320). If thedifference between predetermined test module response and the measuredtest response does exceed the threshold, the UPS module is indicated aspotentially faulty and the UPS module transmits an indication of thesame (block 330). Upon receipt of the diagnostic data/status identifyingthe circuit or UPS module, as potentially faulty, the UPS system controlcircuit 210 may maintain the respective UPS module in the idle state(block 335). Still further, the UPS system control circuit 210 mayretransmit the diagnostic data/status to upper levels of the hierarchy.

If, however, the difference between the predetermined UPS test moduleresponse and the measured test response is less than the threshold value(block 320), a determination is made as to whether the diagnostic testis complete (block 325). If the diagnostic is determined to be complete,the UPS module 205 may exit the idle state under control of the controlcircuit (block 345). It however, the diagnostic is determined not to becomplete, the next diagnostic test in the suite may be selected (block340), and operations continue at block 305.

FIG. 4 is a block diagram illustrating circuits included within the UPSmodule 205 shown in FIG. 2 in some embodiments according to theinvention. According to FIG. 4, the UPS module 205 can provide power tothe load based on the AC input. The power to the load can be providedthrough various mechanisms provided by the UPS module 205. For example,power can be provided to the load via a bypass switch 445, which may beoperative under normal operating conditions when AC power provided, forexample, by a utility can be passed through to the load. Further, powercan be provided to the load through a rectifier circuit 400 which drivesa DC link 410 that is coupled to the input of an inverter circuit 425.The DC link 410 is also coupled to a DC link capacitor, which maintainsthe node A at a DC link voltage at the input of the inverter circuit425.

The inverter circuit 425 drives an output filter 430 which, in turn, canbe switchably coupled to the load via a contactor 435. In particular,the contactor 435 may be open to electrically decouple the load from theUPS module 205. Accordingly, when the contactor 435 is open, the UPSmodule 205 can be in the idle state so that no power is provided to theload by the UPS module 205.

Power can also be provided to the load by a DC-DC converter circuit 415,which receives DC power from a battery 420, which can be associated withthe UPS module 205. It will be understood that the battery 420 can bededicated for use by the UPS module 205 and specifically for use by theDC-DC converter circuit 415. The DC-DC converter circuit 415 canmaintain the DC link 410 at the DC link voltage, so that the rectifiercircuit 425 can provide power to the load via the output filter 430 whenthe AC input is unavailable.

It will be understood that each of the circuits in the UPS module 205can be operatively coupled to a control circuit 450. In operation, thecontrol circuit 450 can monitor operations of the circuits included inthe UPS module 205 and, moreover, can coordinate operation of thediagnostics and status information generated therefrom. For example, insome embodiments according to the invention, the control circuit 450 cancontrol each of the circuits described herein to operate in support ofthe idle state. For example, when the control circuit 450 receivesdiagnostic control information from a higher order control circuit, thecontrol circuit 450 may initiate the idle state for the UPS module 205,so that diagnostics may be carried out. In particular, the controlcircuit 450 can initiate the idle state for the UPS module 205 such thatsome of the circuits included in the module 205 enter a standby modewhich may enable reduced power demand from the respective circuit placedin the standby mode. When the UPS module 205 is placed in the idlestate, the control circuit 450, for example, can initiate testing of theUPS module 205. It will be understood that the tests can vary in scopefrom an overall UPS module test to tests that focus on individualcomponents or subsystems. Further, the tests can vary in what parametersare tested, such as power, voltage, current, etc.

In some embodiments according to the invention, once the idle state isinitiated, a total power drawn by the UPS module 205 may be measured bythe control circuit 450. For example, the control circuit 450 mayprovide AC power at the rectifier circuit 400 as the UPS module testinput and may measure the current and voltage drawn at the AC input todetermine the power used by the UPS module 205 in the idle state (i.e.,the UPS module test response). The control circuit 450 may then comparethe measured power to a predetermined power value that is nominallyassociated with a UPS module known not to be faulty. If the measuredpower in idle state is about equal to the predetermined power used inthe idle state, the control circuit 450 may indicate that the diagnostictest shows that the UPS module 250 is not faulty. It will be understood,however, that the test described above may be only one of a suite ofdiagnostic tests that can be performed on the UPS module 205 to diagnosewhether the UPS module is faulty or not.

It will be understood that each of the components shown in FIG. 4 caninclude transducer circuits and/or sensor circuits that are accessibleto the control circuit 450, to facilitate the measurement of currents,voltages, and other parameters associated with those circuits. Thesetransducers and sensor circuits can therefore provide “metering” for thecontrol circuit 450 so that the circuits and systems in the UPS module205 can be tested by the control circuit 450.

In some embodiments according to the invention, the control circuit 450can test the UPS module by closing the contactor 405. Once the contactor405 is closed, the availability of the AC input will allow thecomponents on the UPS module 205 to draw power from the AC input. Thecontrol circuit 450 can then measure the actual power drawn by all ofthe components on the UPS module 205 in the idle state as the responseto the UPS module test input. It will be understood that even though theUPS module 205 operates in the idle state, many of the componentsincluded in the UPS module 205 will draw current either under control ofthe control circuit 450 or by operating in a standby power mode. In anyevent, each of the components that draws power from the AC input maycontribute to the measured power drawn by the UPS module 205 in the idlestate.

The predetermined power value may be provided by either calculations ordata collected for actual UPS modules of the same type. If the measuredpower drawn at the AC input either exceeds or is less than thepredetermined value, the UPS module may be determined to be faulty. Insome embodiments according to the invention, a threshold value may beestablished to distinguish between allowable variations from thepredetermined value. In other words, the measured power drawn at the ACinput may fall within an acceptable range of the predetermined powervalue. In such cases, the UPS module 205 may still be identified asnon-faulty if the measured power varies from the predetermined value byless than the threshold value. In some embodiments according to theinvention, the threshold can be about +/−10% of the predetermined value.In some embodiments according to the invention, the threshold can bedetermined by statistical data gathered on operating UPS modules or onhistorical data associated with the particular UPS module under testincluding data gathered during manufacturing.

In some embodiments according to the invention, the amount of variationfrom the predetermined power value may indicate which circuit or systemon the UPS module 205 is faulty. Data may be provided that identifiesthe amount of variation from the predetermined power value that may beobserved if particular circuits or systems are faulty. For example, ifthe UPS module 205 includes a faulty fan 440, then the measured powermay vary from the predetermined power value by a known amount. Analogousvalues may be established for other components, such as a faulty powerconversion circuit (e.g., a half bridge IGBT circuit, a power MOSFETcircuit, etc.), a faulty DC link capacitor, a faulty inverter circuit, afaulty rectifier circuit, a faulty DC-DC converter circuit and/or afaulty output filter circuit.

The control circuit 450 may also provide testing of the UPS module 205at a lower level than the UPS module tests described above. For example,in some embodiments according to the invention, the control circuit 450can control the rectifier circuit 400 to charge the DC link 410, andthen measure the voltage of the DC link 410. If the voltage provided onthe DC link 410 varies from a predetermined value for the DC linkvoltage, the rectifier circuit 400 (or the DC link 410) may be faulty.

In some embodiments according to the invention, the control circuit 450can control a precharge circuit 455 to charge and discharge a DC linkcapacitor (including the DC link 410) which is responsible formaintaining the voltage at node A at the input of an inverter circuit425. The control circuit 450 may measure the charge and dischargecharacteristics of the DC link capacitor, which can then be compared topredetermined values for the charging and discharging of the DC linkcapacitor. If the measured parameters vary from the predeterminedvalues, the DC link capacitor or the rectifier circuit 400 may befaulty.

FIGS. 5A and 5B are graphs illustrating charging and dischargingcharacteristics of a capacitor, such as the DC link capacitor, in someembodiments according to the invention. In particular, the parametersshown in FIGS. 5A and 5B can be determined when the control circuit 450activates, for example, the rectifier circuit 400 to charge the DC linkcapacitor and to measure the voltages and times shown in FIGS. 5A and 5Busing the associated expressions therein to determine whether the DClink capacitor is likely faulty using, for example, a calculatedcapacitance for the DC link capacitor based on the measured parameters.

In some embodiments according to the invention, the control circuit 450may activate the DC-DC converter circuit 415 to charge the DC linkcapacitor and the DC link 410. In some embodiments according to theinvention, the control circuit 450 can activate the DC-DC circuit 415and measure the voltage and current provided to the DC link 410 by theDC-DC converter 415 to determine whether the DC-DC converter circuit 415or DC link capacitor 425 is likely faulty.

In some embodiments according to the invention, the control circuit 450can operate the rectifier circuit 400 to charge the DC link capacitor toa specified voltage and measure the power provided to the gate of a halfbridge circuit included in the inverter circuit 425. In particular,insulated-gate bipolar transistors (IGBT) located within the half bridgecircuit in the inverter circuit 425 can be tested by the control circuit450 by providing a power gate signal to the IGBT devices while the UPSmodule is in the idle state. Application of the power gate signal toIGBT devices can be done as described in U.S. Pat. No. 7,583,109 toOughton Jr. et al., the disclosure of which is incorporated herein byreference. Other approaches can also be used. It will be understood,however, that other types of power conversions circuits, such as powerMOSFET circuits may be used in place of the a half bridge circuitincluding the insulated-gate bipolar transistors.

In still further embodiments according to the invention, the controlcircuit 450 can operate the inverter circuit 425 to drive an outputfilter circuit 430 with a predetermined waveform and may measure thevoltage at node B, which can be compared to predetermined parameters fornode B associated with a non-faulty rectified circuit 400, invertercircuit 425 and output filter circuit 430. For example, the invertercircuit 425 or rectifier circuit 400 can be controlled to provide a sinewave voltage to the output filter circuit 430, whereupon the waveform atnode B can be sampled by the control circuit 450, which is sometimesreferred to as a “capacitor bleed-down test.”

FIG. 6 is a graph illustrating bleed-down characteristics of an outputfilter circuit in some embodiments according to the invention. Accordingto FIG. 6, and as described above, a sine wave excitation can beprovided to the inverter circuit 425 by the rectifier circuit 410 orDC-DC converter circuit 415 or the precharge circuit 455. In turn, theinverter circuit 425 can produce the sine wave response shown in FIG. 6via the output filter circuit 430. In particular, the rate of dischargeobserved can provide an indication of the functionality of the invertercircuit 425 or the rectifier circuit 400 and other circuits.

It will be further understood that the capacitor bleed-down describedherein can also be utilized to determine the functionality of the DClink capacitor as well as the rectifier circuit 400. In particular, thecontrol circuit 450 can cause the rectifier circuit 400 to produce thedecaying sine wave output shown in FIG. 6 at the input of the rectifiercircuit 400 as described above in reference to the inverter circuit 425.Accordingly, it will be understood that the DC link capacitor shown inFIG. 4 can be tested by the control circuit 450 using the capacitorbleed-down approach shown in FIG. 6.

In the drawings and specification, there have been disclosed exemplaryembodiments of the inventive subject matter. Although specific terms areemployed, they are used in a generic and descriptive sense only and notfor purposes of limitation, the scope of the inventive subject matterbeing defined by the following claims.

1. An Uninterruptible Power Supply (UPS) module configured for inclusionin a UPS system, the UPS module comprising: a rectifier circuit,switchably coupled to an AC input to the UPS module, configured toprovide a rectified output voltage to a DC link node; a DC-DC convertercircuit, switchably coupled to a back-up power input to the UPS module,configured to provide DC voltage to the DC link node, based on theback-up power input; an inverter circuit, coupled to the DC link node,configured to provide an AC output for the UPS module based on therectified output voltage or the DC voltage; and a control circuitconfigured to activate an idle state for the UPS module, and to providea UPS module test power input to the rectifier circuit, the DC-DCconverter circuit, and/or the inverter circuit, and configured todetermine a UPS module test power response to the UPS module test powerinput, and to compare the UPS module test power response to apredetermined UPS module test power response.
 2. The UPS module of claim1 wherein the control circuit is further configured to identify the UPSmodule as a potentially faulty UPS module responsive to determining thatthe UPS module test power response varies from the predetermined UPSmodule test power response by more than a threshold value.
 3. The UPSmodule of claim 1 wherein the UPS module test power response varies fromthe predetermined UPS module test power response by an amount of powerassociated with a faulty power supply, a faulty fan, a faultyhalf-bridge IGBT circuit in the UPS, a faulty DC link capacitor, afaulty inverter circuit, a faulty rectifier circuit, a faulty DC-DCconverter circuit, a faulty output filter circuit, or any combinationthereof.
 4. The UPS module of claim 1 wherein the UPS module testcontrol response varies from the predetermined UPS module test controlresponse by a predetermined test response or state change associatedwith a control board, control circuit, embedded firmware and/ornon-volatile memory stored parameters, communication circuit or link,fault sensing or telemetry circuit, or any combination thereof.
 5. TheUPS module of claim 1 wherein the control circuit is configured toactivate an idle state for the UPS module, provide the UPS module testpower input to the UPS module in the idle state, provide power to a loadby another UPS module in the UPS system;
 6. The UPS module of claim 5wherein the control circuit is configured to provide, from the UPSmodule in the idle state, a UPS module test response to the UPS moduletest power input and to identify the UPS module as a potentially faultyUPS module responsive to determining that the UPS module test responsevaries from the predetermined UPS module test response by more than athreshold value.
 7. The UPS module of claim 1 wherein the controlcircuit is configured to identify the UPS module as a potentially faultyUPS module by comparing the UPS module test response to a predeterminedUPS module test response and to transmit a service indicator thatidentifies the UPS module as potentially faulty.
 8. The UPS module ofclaim 1 wherein the UPS module test response varies from thepredetermined UPS module test response by an amount associated with afaulty component included in the UPS module, the faulty component beingconfigured to operate when the UPS module is in the idle state.
 9. TheUPS module of claim 1 wherein the control circuit is configured toactivate the idle state for the UPS module by configuring the UPS moduleto provide no power to the load.
 10. The UPS module of claim 9 whereincontrol circuit is configured to provide no power to the load by openinga contactor located between the load and the inverter circuit or byelectrically isolating an output of the rectifier circuit from the load.11. The UPS module of claim 9 wherein control circuit is configured toprevent the UPS module from providing power to the load responsive toidentifying the UPS module as the potentially faulty UPS module.
 12. TheUPS module of claim 1 wherein control circuit is configured to identifythe UPS module as a functional UPS module responsive to determining thatthe UPS module test response varies from the predetermined UPS moduletest response by less than the threshold value and configured todeactivate the idle state for the UPS module.
 13. The UPS module ofclaim 1 wherein the control circuit is configured to activate the idlestate for the UPS module by activating the idle state for a first UPSmodule responsive to determining that a second UPS module included inthe UPS system is configured to provide the power to the load, while thefirst UPS module is in the idle state.
 14. The UPS module of claim 1wherein the control circuit is configured to provide the UPS module testinput to the UPS module in the idle state by applying an ac input to arectifier circuit included in the UPS module; and wherein the controlcircuit is configured to provide, from the UPS module in the idle state,the UPS module test response by determining power provided to therectifier circuit by the ac input in response to applying the ac input.15. The UPS module of claim 1 wherein the control circuit is configuredto provide the UPS module test input to the UPS module in the idle stateby applying a test gate signal to a gate terminal of an IGBT deviceincluded in a half-bridge circuit in the inverter circuit when the UPSmodule is in the idle state; and wherein the control circuit isconfigured to provide, from the UPS module in the idle state, the UPSmodule test response by determining a power at the gate terminal inresponse to applying the test gate signal.
 16. The UPS module of claim 1wherein the control circuit is configured to provide the UPS module testinput to the UPS module in the idle state by charging/discharging the DClink node of a capacitor at an input of the inverter circuit when theUPS module is in the idle state; and wherein the control circuit isconfigured to provide, from the UPS module in the idle state, the UPSmodule test response by determining a capacitance of the capacitor basedon the charging/discharging the DC link node.
 17. The UPS module ofclaim 16 wherein the control circuit is configured to charge/dischargethe DC link node by charging/discharging the DC link node using aprecharge circuit coupled to the AC input.
 18. The UPS module of claim16 wherein the control circuit is configured to charge/discharge the DClink node by charging/discharging the DC link node using the DC-DCconverter circuit coupled to a battery associated with the UPS module.19. The UPS module of claim 16 wherein the control circuit is configuredto charge/discharge the DC link node by charging/discharging the DC linknode using the rectifier circuit coupled to the AC input.
 20. The UPSmodule of claim 1 wherein the control circuit is configured to providethe UPS module test input to the UPS module in the idle state byproviding an input signal to a filter circuit coupled to an output ofthe inverter circuit, when the UPS module is in the idle state; andwherein the control circuit is configured to provide, from the UPSmodule in the idle state, the UPS module test response by determining aresponse from the filter circuit generated by the input signal.